1. Technical Field
This invention relates to the electric generation of steam for use in domestic irons, steam cleaners, wallpaper strippers and other hand-held steam generating appliances.
2. Background Information
Domestic steam irons have been around for a long time. They comprise a sole plate which is flat and intended to contact the item to be ironed and which is normally heated by means of a sheathed electrical resistance heater mounted to or embedded in the upper side of the sole plate. Traditionally, such irons which are designed to produce steam in order to improve ironing have a semi-closed cavity formed on the upper face of the sole plate and into which water is dripped from an on-board reservoir to produce steam which is then allowed to escape onto the clothes by means of a series of apertures formed in the sole plate. These are commonly known as vented steam irons. They are relatively simple and inexpensive to implement which has made them very popular. However, the steam produced is at very low pressure (essentially ambient pressure) and cannot be produced very quickly, making it relatively ineffective.
At the other end of the market, are professional or semi-professional steam ironing systems in which high pressure steam (e.g. of the order of 3 to 5 bar) is continuously produced in a static base station incorporating a large water reservoir which can then be fed, on demand, to the user's hand-held unit by means of an umbilical cord. These are commonly known as pressurized steam generator irons. They deliver a very high performance but are very expensive and tend to account therefore only for a very small proportion of the market.
More recently there have been proposals, some of which have been commercialized, which seek to bridge the gap between the two extremes outlined above, although these have tended to carry their own drawbacks. For example, it has been proposed to provide a boiler in a base unit, separate from the iron, which is fed by pumping water into it from a reservoir in the base station. The main disadvantage with these arrangements, commonly known as instantaneous steam generator irons, is that there is in fact a significant time lag (of the order of 10 seconds) between the user pressing a button to demand steam and the steam actually being produced and conveyed to the iron. This significantly limits user acceptance, even though higher steam flow rates than vented steam irons can be achieved when the steam is eventually delivered.
It is an aim of the present invention to provide an improved arrangement for generating steam on demand which can be used in steam irons, but also in other devices employing steam, such as steam cleaners, wallpaper strippers, other hand-held steam generating appliances etc.